The present invention relates to a method for preparing small spherical particles which consist entirely or partly of at least one water-insoluble linear polysaccharide and also to particles obtainable by this method.
The applicant""s German patent application No. 19737481.6 which has earlier priority but is not a prior publication describes methods for preparing spherical microparticles containing water-insoluble linear polysaccharides. This method can produce spherical microparticles which stand out in particular due to high uniformity with respect to their shape and their diameter distribution and also due to good mechanical properties. Owing to their comparatively uniform constitution and with simultaneously good mechanical properties, these particles may be employed for a multiplicity of applications.
It has, however, become apparent that, depending on the intended application, a specific optimization of particular particle properties may be desirable.
The abovementioned method can in particular produce particles with an average diameter of generally 1 xcexcm or greater. There has been a need therefore to develop an optimized method which may be used for specifically preparing small particles whose average diameter does not exceed a few micrometers and is in particular in the nanometer range.
It was therefore an object of the present invention to provide a method which can be used for reproducibly producing in a simple manner water-insoluble spherical particles which contain linear polysaccharides and which have, aside from a regular shape, uniform diameter distribution and also good mechanical properties, a particularly small average diameter which does not exceed a few micrometers and which is preferably in the nanometer range.
This object is achieved by a method for preparing small spherical particles which consist entirely or partly of at least one water-insoluble linear polysaccharide by dissolving the at least one water-insoluble linear polysaccharide in a solvent or solvent mixture, introducing the solution formed into a precipitant or precipitant mixture, where appropriate cooling the mixture being produced in the process and removing the particles formed, wherein at least one hot-water-soluble poly-alpha-D-glucan is used as a precipitation aid.
The present invention further relates to small spherical particles as obtainable according to the abovementioned method.
In this respect, the present invention means an advantageous inventive development of the abovementioned German patent application No. 19737481.6 whose contents are incorporated in their entirety by way of reference for the purposes of the present invention.
Although said application also discusses the use of precipitation aids, there is no information on the use of hot-water-soluble poly-alpha-D-glucan, in particular no information on using such compounds in order to specifically control the size of the particles.